Conventionally, barrier layers, usually in a form of innerliners, for pneumatic rubber tires are comprised of butyl or halogenated butyl rubber (e.g. halobutyl rubber) layers which have greater resistance to air, oxygen, and nitrogen permeability than other tire components. Such barrier layers, or innerliners, are provided to inhibit the loss of air or oxygen from the pneumatic tire cavity through the barrier layer into the tire carcass which promotes retention of air, including retention of air pressure, within the pneumatic tire cavity. In order to provide a suitable degree of air or oxygen impermeability, such innerliner layer needs to be sufficiently thick so that it adds significant weight to the tire. Further, an additional rubber layer, sometimes referred to as a tie layer, with low hysteresis loss, added in a manner that it is sandwiched between the barrier layer and the tire carcass.
The thickness of the butyl rubber (e.g. halobutyl rubber) adds significantly to the weight of the tire. Accordingly, alternate thinner materials with low air or oxygen permeability are desired, particularly in a form of thin films, for use as such barrier layers. Various candidates which are relatively impermeable to air or oxygen have heretofore been proposed, including, for example, polyvinylidene chloride, nylon, and polyester. For example, see U.S. Pat. Nos. 5,040,583, 4,928,741. Composites containing such films have been proposed such as, for example, at least one layer of a thin film of such non-elastomeric barrier material sandwiched and bonded between two elastomer layers of elastomeric compositions. Thin films of alloys with a resistance to air and/or oxygen permeability have also been proposed for a tire innerliner layer comprised of a mixture of thermoplastic resin, elastomer and, optionally, a binder resin to enhance the compatibility between the thermoplastic resins and elastomers.
There remains a need for an innerliner material that can be significantly thinner than their conventional butyl rubber-based counterpart tire innerliners and can therefore provide a substantial tire weight savings.